This invention is generally directed to layered photoresponsive imaging members, and more specifically to photoconductive imaging members having incorporated therein certain indigoid compounds. In one embodiment of the present invention, there is provided organic photoconductive layered imaging members comprised of certain indigoid compounds and aryl amine hole transport layers. Further, in one important embodiment of the present invention, there is provided a photoresponsive imaging member or device comprised of vacuum evaporated fractionally sublimed indigoids selected from 4,4',7,7'-tetrachlorothioindigo and the derivatives thereof; and an aryl amine hole transport layer. The aforementioned photoconductive members possess a number of advantages as indicated herein inclusive of high photosensitivity, low residual potentials, low dark decay characteristics, and stable cycling properties. The photoresponsive imaging members of the present invention can be selected for various electrophotographic imaging and printing processes wherein, for example, latent images are formed thereon followed by development and transfer to a suitable substrate.
Illustrated in U.S. Pat. No. 3,839,034 are organic double layered electrophotographic recording materials consisting of an electroconductive support and a photoconductive double layer of organic indigoid materials which consist of a homogeneous, opaque, charge carrier producing dyestuff layer of the formula as illustrated in the Abstract of the Disclosure, and the formulas of FIGS. 1 to 17, the formulas of FIGS. 2, 3, 7, and 15 being of particular interest; and a transparent top layer of insulating materials with at least one charge transporting compound. Further, as indicated in column 4, lines 1 to 22, as the Formula 7 compound for the imaging member of the '034 patent there can be selected permanent Red Violet MR (Pigment Red 88). Moreover, it is stated in column 4, beginning at around line 30, that the dyestuff layer may be applied by the vapor deposition thereof in a vacuum. Moreover, this patent discloses a number of resinous binders for the charge transport layer including polycarbonate resins, reference column 6. Since the charge carrier dyestuffs selected for the members of this patent are not fractionally sublimed, there remains therein impurities that can adversely affect the characteristics thereof, including photosensitivity, dark decay, and image quality depending on the impurities present, for example. Prior art primarily of background interest include U.S. Pat. Nos. 4,264,694; 4,606,987; and 4,622,278.
Furthermore, in Konishiroku Kokai Japanese No. 54/1395401A1[79/1030] there is disclosed the use of selected indigoids as charge generator layers in conjunction with triphenyl methane charge transport layers. Specifically, a solution coated dispersion of 4,4',7,7'-tetrachlorothioindigo in a polymer binder can be selected as the charge generator layer. Also, in U.S. Pat. No. 3,850,630 there are disclosed imaging members with dichloro substituted thioindigo vacuum coated charge generator layers contiguous with poly(vinyl carbazole) or 2,4,7-trinitro-9-fluorenone charge transport layers.
Additionally, numerous different xerographic photoconductive members are known including, for example, a homogeneous layer of a single material such as vitreous selenium, or a composite layered device containing a dispersion of a photoconductive composition. An example of one type of composite xerographic photoconductive member is described, for example, in U.S. Pat. No. 3,121,006 wherein there is disclosed finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. These members contain, for example, coated on a paper backing a binder layer containing particles of zinc oxide uniformly dispersed therein. The binder materials disclosed in this patent comprise a material such as polycarbonate resins, polyester resins, polyamide resins, and the like, which are incapable of transporting for any significant distance injected charge carriers generated by the photoconductive particles. Accordingly, as a result the photoconductive particles must be in a substantially contiguous particle to particle contact throughout the layer for the purpose of permitting charge dissipation required for a cyclic operation.
There are also known photoreceptor materials comprised of inorganic or organic materials wherein the charge carrier generating, and charge carrier transport functions are accomplished by discrete contiguous layers. Additionally, layered photoreceptor materials are disclosed in the prior art which include an overcoating layer of an electrically insulating polymeric material. However, the art of xerography continues to advance and more stringent demands need to be met by the copying apparatus in order to increase performance standards, and to obtain quality images.
Also, there have been disclosed other layered photoresponsive devices including those comprised of separate generating layers, and transport layers as described in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Examples of photogenerating layers disclosed in this patent include trigonal selenium and phthalocyanines, while examples of transport layers include certain diamines as mentioned herein.
Many other patents are in existence describing photoresponsive devices including layered devices containing generating substances, such as U.S. Pat. No. 3,041,167 which discloses an overcoated imaging member containing a conductive substrate, a photoconductive layer, and an overcoating layer of an electrically insulating polymeric material. This member is utilized in an electrophotographic copying system by, for example, initially charging the member with an electrostatic charge of a first polarity, and imagewise exposing to form an electrostatic latent image, which can be subsequently developed to form a visible image.
Furthermore, there are disclosed in U.S. Pat. Nos. 4,232,102 and 4,233,383 photoresponsive imaging members comprised of trigonal selenium doped with sodium carbonate, sodium selenite, and trigonal selenium doped with barium carbonate, and barium selenite, or mixtures thereof. Moreover, there are disclosed in U.S. Pat. No. 3,824,099 certain photosensitive hydroxy squaraine compositions. According to the disclosure of this patent, the squaraine compositions are photosensitive in normal electrostatographic imaging systems.
Also known are photoconductive devices containing therein various squaraine compositions. Thus, for example, there is illustrated in U.S. Pat. No. 4,508,803, the disclosure of which is totally incorporated herein by reference, photoconductive devices containing novel benzyl fluorinated squaraine compositions. Specifically, in one embodiment illustrated in the '803 patent there is described an improved photoresponsive device comprised of a supporting substrate, a hole blocking layer, an optional adhesive interface layer, an inorganic photogenerating layer, a photoconducting composition layer comprised of benzyl fluorinated squaraine compositions, and a hole transport layer. Other representative patents disclosing photoconductive devices with squaraine components therein, or processes for the preparation of squaraines include U.S. Pat. Nos. 4,507,408; 4,552,822; 4,559,286; 4,507,480; 4,524,220; 4,524,219; 4,524,218; 4,525,592; 4,559,286; 4,415,639; 4,471,041; and 4,486,520. The disclosures of each of the aforementioned patents are totally incorporated herein by reference.
Moreover, disclosed in the published literature are composite electrophotographic photosensitive materials with various azo compounds. For example, there is illustrated in Japanese Ricoh Patent Publication No. 6064354, published Apr. 12, 1985, composite photoconductors wherein one of the photoconductor layers contains an azo compound of the formulas as illustrated. Further, there are illustrated in several U.S. patents illustrative layered organic electrophotographic photoconductor elements with azo, bisazo, or related compounds. Examples of these patents include Nos. 4,400,455; 4,551,404; 4,390,608; 4,327,168; 4,299,896; 4,314,015; 4,486,522; 4,486,519; 4,551,404; and Konishiroku Japanese Patent Laid Open Publication No. 60111247.
Although photoconductive imaging members are known, there remains a need for members with other photogenerator layers. Additionally, there continues to be a need for layered photoresponsive imaging members having incorporated therein certain indigoid compounds, which members will enable the generation of acceptable high quality images, and wherein these members can be repeatedly used in a number of imaging cycles without deterioration thereof from the machine environment or surrounding conditions. Moreover, there is a need for improved layered photoresponsive imaging members wherein the indigoid compounds selected for one of the layers in combination with specific aryl amine charge transport compositions are substantially inert to the users of such members. Additionally, there is an important need for layered photoconductors with indigoid compounds, which photoconductors are of high sensitivity, have low dark decay values, low residual potentials, and possess high cyclic stability. Furthermore, there continues to be a need for photoresponsive imaging members which can be positively or negatively charged thus permitting the development of images, including color images, with positively or negatively charged toner compositions. Moreover, there continues to be an important need for disposable imaging members with nontoxic organic pigments. Also, there is a need for disposable imaging members useful in xerographic imaging processes, and xerographic printing systems wherein, for example, light emitting diodes (LED), helium cadmium, or helium-neon lasers can be selected; and wherein these members are particularly sensitive to the visible region of the spectrum, that is from about 400 to about 700 nanometers. Also, there is a need for low cost, high quality imaging members wherein reduced amounts of photosensitive materials can be selected. Additionally, there is a need for imaging members with vacuum evaporated fractionally sublimed indigoid compounds, which compounds are substantially free of undesirable impurities.